The present invention relates to an improved antitheft alarm system for a car and an electronic device mounted in the car.
In order to prevent a theft of a car stereo and other electronic devices provided in the car, there has been made many proposals. In accordance with one of the proposals, a removable panel having a plurality of push button, keys and a display for controlling the stereo is attached to the body of the stereo. When the removable panel is attached to the body, a circuit provided therein is electrically connected to a circuit in the body, thereby enabling the car stereo to operate. The body is totally useless unless the panel is attached. Hence, if the driver takes the panel with him when leaving the car, the theft of the car stereo can be prevented.
In accordance with another proposed system, a car stereo is provided with means for registering an identification code. The user, when leaving the car, stores an arbitrary code in a memory provided in the car stereo by operating a ten-key keyboard which is used for designating songs to be played on the car stereo. If the car stereo is stolen from the car, a control unit provided in the car stereo determines that the car stereo is disconnected from a power supply. When the car stereo is again applied with power, the car stereo cannot be operated unless the code is input.
Some cars are provided with antitheft systems for preventing the theft of the car. The system is operatively connected to a door of the car. When the door is opened by a means other than a key of the owner, the car horn emits an alarming sound.
In order to prevent the theft of both the car stereo and the car itself, a system for each must be provided. Thus the antitheft systems become complicated and also the cost is increased. In addition, the systems takes up a space in the interior of the car. Moreover, the driver must carry out complicated operations to set and release the alarm which takes time. There is a further possibility of the driver forgetting the procedure for operating one of these systems.
The applicant of the present invention has disclosed in Japanese Patent Application No. 7-168019, an antitheft alarm system of a car and a car stereo mounted in the car, wherein the alarm mode is easily set by removing a panel of the car stereo from a body thereof. The alarm is activated unless the panel is attached or when the ignition key is operated within a predetermined time after the door of the car is opened for entry. Since most of the cars are now equipped with a car stereo, the system is quite effective.
The conventional alarm system determines the entry of the legitimate user only when an releasing operation such as the attaching of the panel and turning of the ignition key is carried out within a predetermined period. The legitimate user is often startled by the unexpected sounding of alarm when the releasing operation is forgotten or delayed. In addition, the car stereo cannot be stolen if the intrusion into the car itself is prevented in the first place. Hence it is not necessary to use the detachable panel in the alarm system.
Moreover, the alarm system is ineffective against intrusion without the opening of the door, namely, through windows, and vandalistic criminal act, such as smashing and striking of the car from the outside, which do not necessarily result in the theft of the car.